SPI SM-01047 Indexing Washer Kit 2 Cylinder8/pk

Indexed spark plugs align the open end of the electrode toward the intake port.  The hottest flame meets the new fuel charge for a performance gain, increases fuel mileage and plug life.  This is a speed secret car racers have used for years.  You simply mark the electrode side of the plug with a magic marker on the porcelain.  You then shim the plugs with the washers to align the electrodes toward the intake ports.